Nonlinear optical effects in polycrystalline transparent Al₂O₃ ceramics using femtosecond laser pulses-supercontinuum generation and laser damage

Nonlinear optical properties play a key role in technologies such as broadband laser light sources and ultrafast laser machining. With the emergence of transparent nanocrystalline Al2O3 ceramics as an alternative to single crystal alumina (sapphire), it is critical to understand their nonlinear optical behavior. Here, we report the demonstration of supercontinuum generation in polycrystalline alumina ceramics. Substantial broadening was observed when a focused 515 nm pulsed (260 fs) laser propagated through the ceramic sample. The broadening increased with increasing laser power and displayed stokes/anti-stokes asymmetries. At higher incident power, permanent damage was observed. Our results show that transparent nanocrystalline Al2O3 ceramics have a higher material removal rate than single crystal alumina. These results have interesting implications for laser machining as well as integrated photonics.